1 IntroductionSoftware testingSoftware testing is an investigation conducted to provide stakeholders with information about the quality of theproduct or service under test. Software testing can also provide an objective, independent view of the software toallow the business to appreciate and understand the risks of software implementation. Test techniques include, butare not limited to, the process of executing a program or application with the intent of finding software bugs (errorsor other defects).Software testing can be stated as the process of validating and verifying that a software program/application/product:1. meets the requirements that guided its design and development;2. works as expected; and3. can be implemented with the same characteristics.Software testing, depending on the testing method employed, can be implemented at any time in the developmentprocess. However, most of the test effort occurs after the requirements have been defined and the coding process hasbeen completed. As such, the methodology of the test is governed by the software development methodologyadopted.Different software development models will focus the test effort at different points in the development process.Newer development models, such as Agile, often employ test driven development and place an increased portion ofthe testing in the hands of the developer, before it reaches a formal team of testers. In a more traditional model, mostof the test execution occurs after the requirements have been defined and the coding process has been completed.OverviewTesting can never completely identify all the defects within software. Instead, it furnishes a criticism orcomparison that compares the state and behavior of the product against oracles—principles or mechanisms by whichsomeone might recognize a problem. These oracles may include (but are not limited to) specifications, contracts,comparable products, past versions of the same product, inferences about intended or expected purpose, user orcustomer expectations, relevant standards, applicable laws, or other criteria.Every software product has a target audience. For example, the audience for video game software is completelydifferent from banking software. Therefore, when an organization develops or otherwise invests in a softwareproduct, it can assess whether the software product will be acceptable to its end users, its target audience, itspurchasers, and other stakeholders. Software testing is the process of attempting to make this assessment.A study conducted by NIST in 2002 reports that software bugs cost the U.S. economy $59.5 billion annually. Morethan a third of this cost could be avoided if better software testing was performed.HistoryThe separation of debugging from testing was initially introduced by Glenford J. Myers in 1979. Although hisattention was on breakage testing ("a successful test is one that finds a bug"  ) it illustrated the desire of thesoftware engineering community to separate fundamental development activities, such as debugging, from that ofverification. Dave Gelperin and William C. Hetzel classified in 1988 the phases and goals in software testing in thefollowing stages:• Until 1956 - Debugging oriented
Software testing 2 • 1957–1978 - Demonstration oriented • 1979–1982 - Destruction oriented • 1983–1987 - Evaluation oriented • 1988–2000 - Prevention oriented Software testing topics Scope A primary purpose of testing is to detect software failures so that defects may be discovered and corrected. This is a non-trivial pursuit. Testing cannot establish that a product functions properly under all conditions but can only establish that it does not function properly under specific conditions. The scope of software testing often includes examination of code as well as execution of that code in various environments and conditions as well as examining the aspects of code: does it do what it is supposed to do and do what it needs to do. In the current culture of software development, a testing organization may be separate from the development team. There are various roles for testing team members. Information derived from software testing may be used to correct the process by which software is developed. Functional vs non-functional testing Functional testing refers to activities that verify a specific action or function of the code. These are usually found in the code requirements documentation, although some development methodologies work from use cases or user stories. Functional tests tend to answer the question of "can the user do this" or "does this particular feature work". Non-functional testing refers to aspects of the software that may not be related to a specific function or user action, such as scalability or other performance, behavior under certain constraints, or security. Non-functional requirements tend to be those that reflect the quality of the product, particularly in the context of the suitability perspective of its users. Defects and failures Not all software defects are caused by coding errors. One common source of expensive defects is caused by requirement gaps, e.g., unrecognized requirements, that result in errors of omission by the program designer. A common source of requirements gaps is non-functional requirements such as testability, scalability, maintainability, usability, performance, and security. Software faults occur through the following processes. A programmer makes an error (mistake), which results in a defect (fault, bug) in the software source code. If this defect is executed, in certain situations the system will produce wrong results, causing a failure. Not all defects will necessarily result in failures. For example, defects in dead code will never result in failures. A defect can turn into a failure when the environment is changed. Examples of these changes in environment include the software being run on a new hardware platform, alterations in source data or interacting with different software. A single defect may result in a wide range of failure symptoms.
Software testing 3 Finding faults early It is commonly believed that the earlier a defect is found the cheaper it is to fix it. The following table shows the cost of fixing the defect depending on the stage it was found. For example, if a problem in the requirements is found only post-release, then it would cost 10–100 times more to fix than if it had already been found by the requirements review. Cost to fix a defect Time detected Requirements Architecture Construction System test Post-release Time introduced Requirements 1× 3× 5–10× 10× 10–100× Architecture - 1× 10× 15× 25–100× Construction - - 1× 10× 10–25× Compatibility A common cause of software failure (real or perceived) is a lack of compatibility with other application software, operating systems (or operating system versions, old or new), or target environments that differ greatly from the original (such as a terminal or GUI application intended to be run on the desktop now being required to become a web application, which must render in a web browser). For example, in the case of a lack of backward compatibility, this can occur because the programmers develop and test software only on the latest version of the target environment, which not all users may be running. This results in the unintended consequence that the latest work may not function on earlier versions of the target environment, or on older hardware that earlier versions of the target environment was capable of using. Sometimes such issues can be fixed by proactively abstracting operating system functionality into a separate program module or library. Input combinations and preconditions A very fundamental problem with software testing is that testing under all combinations of inputs and preconditions (initial state) is not feasible, even with a simple product.  This means that the number of defects in a software product can be very large and defects that occur infrequently are difficult to find in testing. More significantly, non-functional dimensions of quality (how it is supposed to be versus what it is supposed to do)—usability, scalability, performance, compatibility, reliability—can be highly subjective; something that constitutes sufficient value to one person may be intolerable to another. Static vs. dynamic testing There are many approaches to software testing. Reviews, walkthroughs, or inspections are considered as static testing, whereas actually executing programmed code with a given set of test cases is referred to as dynamic testing. Static testing can be (and unfortunately in practice often is) omitted. Dynamic testing takes place when the program itself is used for the first time (which is generally considered the beginning of the testing stage). Dynamic testing may begin before the program is 100% complete in order to test particular sections of code (modules or discrete functions). Typical techniques for this are either using stubs/drivers or execution from a debugger environment. For example, spreadsheet programs are, by their very nature, tested to a large extent interactively ("on the fly"), with results displayed immediately after each calculation or text manipulation.
Software testing 4 Software verification and validation Software testing is used in association with verification and validation: • Verification: Have we built the software right? (i.e., does it match the specification). • Validation: Have we built the right software? (i.e., is this what the customer wants). The terms verification and validation are commonly used interchangeably in the industry; it is also common to see these two terms incorrectly defined. According to the IEEE Standard Glossary of Software Engineering Terminology: Verification is the process of evaluating a system or component to determine whether the products of a given development phase satisfy the conditions imposed at the start of that phase. Validation is the process of evaluating a system or component during or at the end of the development process to determine whether it satisfies specified requirements. The software testing team Software testing can be done by software testers. Until the 1980s the term "software tester" was used generally, but later it was also seen as a separate profession. Regarding the periods and the different goals in software testing, different roles have been established: manager, test lead, test designer, tester, automation developer, and test administrator. Software quality assurance (SQA) Though controversial, software testing is a part of the software quality assurance (SQA) process. In SQA, software process specialists and auditors are concerned for the software development process rather than just the artifacts such as documentation, code and systems. They examine and change the software engineering process itself to reduce the amount of faults that end up in the delivered software: the so-called defect rate. What constitutes an "acceptable defect rate" depends on the nature of the software; A flight simulator video game would have much higher defect tolerance than software for an actual airplane. Although there are close links with SQA, testing departments often exist independently, and there may be no SQA function in some companies. Software testing is a task intended to detect defects in software by contrasting a computer programs expected results with its actual results for a given set of inputs. By contrast, QA (quality assurance) is the implementation of policies and procedures intended to prevent defects from occurring in the first place. Testing methods The box approach Software testing methods are traditionally divided into white- and black-box testing. These two approaches are used to describe the point of view that a test engineer takes when designing test cases. White box testing White box testing is when the tester has access to the internal data structures and algorithms including the code that implement these. Types of white box testing The following types of white box testing exist: • API testing (application programming interface) - testing of the application using public and private APIs
Software testing 5 • Code coverage - creating tests to satisfy some criteria of code coverage (e.g., the test designer can create tests to cause all statements in the program to be executed at least once) • Fault injection methods - improving the coverage of a test by introducing faults to test code paths • Mutation testing methods • Static testing - White box testing includes all static testing Test coverage White box testing methods can also be used to evaluate the completeness of a test suite that was created with black box testing methods. This allows the software team to examine parts of a system that are rarely tested and ensures that the most important function points have been tested. Two common forms of code coverage are: • Function coverage, which reports on functions executed • Statement coverage, which reports on the number of lines executed to complete the test They both return a code coverage metric, measured as a percentage. Black box testing Black box testing treats the software as a "black box"—without any knowledge of internal implementation. Black box testing methods include: equivalence partitioning, boundary value analysis, all-pairs testing, fuzz testing, model-based testing, exploratory testing and specification-based testing. Specification-based testing: Specification-based testing aims to test the functionality of software according to the applicable requirements. Thus, the tester inputs data into, and only sees the output from, the test object. This level of testing usually requires thorough test cases to be provided to the tester, who then can simply verify that for a given input, the output value (or behavior), either "is" or "is not" the same as the expected value specified in the test case. Specification-based testing is necessary, but it is insufficient to guard against certain risks. Advantages and disadvantages: The black box tester has no "bonds" with the code, and a testers perception is very simple: a code must have bugs. Using the principle, "Ask and you shall receive," black box testers find bugs where programmers do not. On the other hand, black box testing has been said to be "like a walk in a dark labyrinth without a flashlight," because the tester doesnt know how the software being tested was actually constructed. As a result, there are situations when (1) a tester writes many test cases to check something that could have been tested by only one test case, and/or (2) some parts of the back-end are not tested at all. Therefore, black box testing has the advantage of "an unaffiliated opinion", on the one hand, and the disadvantage of "blind exploring", on the other.  Grey box testing Grey box testing (American spelling: gray box testing) involves having knowledge of internal data structures and algorithms for purposes of designing the test cases, but testing at the user, or black-box level. Manipulating input data and formatting output do not qualify as grey box, because the input and output are clearly outside of the "black-box" that we are calling the system under test. This distinction is particularly important when conducting integration testing between two modules of code written by two different developers, where only the interfaces are exposed for test. However, modifying a data repository does qualify as grey box, as the user would not normally be able to change the data outside of the system under test. Grey box testing may also include reverse engineering to determine, for instance, boundary values or error messages.
Software testing 6 Testing levels Tests are frequently grouped by where they are added in the software development process, or by the level of specificity of the test. The main levels during the development process as defined by the SWEBOK guide are unit-, integration-, and system testing that are distinguished by the test target without implying a specific process model. Other test levels are classified by the testing objective. Test target Unit testing Unit testing refers to tests that verify the functionality of a specific section of code, usually at the function level. In an object-oriented environment, this is usually at the class level, and the minimal unit tests include the constructors and destructors. These types of tests are usually written by developers as they work on code (white-box style), to ensure that the specific function is working as expected. One function might have multiple tests, to catch corner cases or other branches in the code. Unit testing alone cannot verify the functionality of a piece of software, but rather is used to assure that the building blocks the software uses work independently of each other. Unit testing is also called component testing. Integration testing Integration testing is any type of software testing that seeks to verify the interfaces between components against a software design. Software components may be integrated in an iterative way or all together ("big bang"). Normally the former is considered a better practice since it allows interface issues to be localised more quickly and fixed. Integration testing works to expose defects in the interfaces and interaction between integrated components (modules). Progressively larger groups of tested software components corresponding to elements of the architectural design are integrated and tested until the software works as a system. System testing System testing tests a completely integrated system to verify that it meets its requirements. System integration testing System integration testing verifies that a system is integrated to any external or third-party systems defined in the system requirements. Objectives of testing Regression testing Regression testing focuses on finding defects after a major code change has occurred. Specifically, it seeks to uncover software regressions, or old bugs that have come back. Such regressions occur whenever software functionality that was previously working correctly stops working as intended. Typically, regressions occur as an unintended consequence of program changes, when the newly developed part of the software collides with the previously existing code. Common methods of regression testing include re-running previously run tests and checking whether previously fixed faults have re-emerged. The depth of testing depends on the phase in the release process and the risk of the added features. They can either be complete, for changes added late in the release or deemed to be risky, to very shallow, consisting of positive tests on each feature, if the changes are early in the release or deemed to be of low risk.
Software testing 7 Acceptance testing Acceptance testing can mean one of two things: 1. A smoke test is used as an acceptance test prior to introducing a new build to the main testing process, i.e. before integration or regression. 2. Acceptance testing is performed by the customer, often in their lab environment on their own hardware, is known as user acceptance testing (UAT). Acceptance testing may be performed as part of the hand-off process between any two phases of development. Alpha testing Alpha testing is simulated or actual operational testing by potential users/customers or an independent test team at the developers site. Alpha testing is often employed for off-the-shelf software as a form of internal acceptance testing, before the software goes to beta testing. Beta testing Beta testing comes after alpha testing and can be considered a form of external user acceptance testing. Versions of the software, known as beta versions, are released to a limited audience outside of the programming team. The software is released to groups of people so that further testing can ensure the product has few faults or bugs. Sometimes, beta versions are made available to the open public to increase the feedback field to a maximal number of future users. Non-functional testing Special methods exist to test non-functional aspects of software. In contrast to functional testing, which establishes the correct operation of the software (correct in that it matches the expected behavior defined in the design requirements), non-functional testing verifies that the software functions properly even when it receives invalid or unexpected inputs. Software fault injection, in the form of fuzzing, is an example of non-functional testing. Non-functional testing, especially for software, is designed to establish whether the device under test can tolerate invalid or unexpected inputs, thereby establishing the robustness of input validation routines as well as error-handling routines. Various commercial non-functional testing tools are linked from the software fault injection page; there are also numerous open-source and free software tools available that perform non-functional testing. Software performance testing and load testing Performance testing is executed to determine how fast a system or sub-system performs under a particular workload. It can also serve to validate and verify other quality attributes of the system, such as scalability, reliability and resource usage. Load testing is primarily concerned with testing that can continue to operate under a specific load, whether that be large quantities of data or a large number of users. This is generally referred to as software scalability. The related load testing activity of when performed as a non-functional activity is often referred to as endurance testing. Volume testing is a way to test functionality. Stress testing is a way to test reliability. Load testing is a way to test performance. There is little agreement on what the specific goals of load testing are. The terms load testing, performance testing, reliability testing, and volume testing, are often used interchangeably.
Software testing 8 Stability testing Stability testing checks to see if the software can continuously function well in or above an acceptable period. This activity of non-functional software testing is often referred to as load (or endurance) testing. Usability testing Usability testing is needed to check if the user interface is easy to use and understand. It is concerned mainly with the use of the application. Security testing Security testing is essential for software that processes confidential data to prevent system intrusion by hackers. Internationalization and localization The general ability of software to be internationalized and localized can be automatically tested without actual translation, by using pseudolocalization. It will verify that the application still works, even after it has been translated into a new language or adapted for a new culture (such as different currencies or time zones). Actual translation to human languages must be tested, too. Possible localization failures include: • Software is often localized by translating a list of strings out of context, and the translator may choose the wrong translation for an ambiguous source string. • Technical terminology may become inconsistent if the project is translated by several people without proper coordination or if the translator is imprudent. • Literal word-for-word translations may sound inappropriate, artificial or too technical in the target language. • Untranslated messages in the original language may be left hard coded in the source code. • Some messages may be created automatically at run time and the resulting string may be ungrammatical, functionally incorrect, misleading or confusing. • Software may use a keyboard shortcut which has no function on the source languages keyboard layout, but is used for typing characters in the layout of the target language. • Software may lack support for the character encoding of the target language. • Fonts and font sizes which are appropriate in the source language, may be inappropriate in the target language; for example, CJK characters may become unreadable if the font is too small. • A string in the target language may be longer than the software can handle. This may make the string partly invisible to the user or cause the software to crash or malfunction. • Software may lack proper support for reading or writing bi-directional text. • Software may display images with text that wasnt localized. • Localized operating systems may have differently-named system configuration files and environment variables and different formats for date and currency. To avoid these and other localization problems, a tester who knows the target language must run the program with all the possible use cases for translation to see if the messages are readable, translated correctly in context and dont cause failures.
Software testing 9 Destructive testing Destructive testing attempts to cause the software or a sub-system to fail, in order to test its robustness. The testing process Traditional CMMI or waterfall development model A common practice of software testing is that testing is performed by an independent group of testers after the functionality is developed, before it is shipped to the customer. This practice often results in the testing phase being used as a project buffer to compensate for project delays, thereby compromising the time devoted to testing. Another practice is to start software testing at the same moment the project starts and it is a continuous process until the project finishes. Agile or Extreme development model In counterpoint, some emerging software disciplines such as extreme programming and the agile software development movement, adhere to a "test-driven software development" model. In this process, unit tests are written first, by the software engineers (often with pair programming in the extreme programming methodology). Of course these tests fail initially; as they are expected to. Then as code is written it passes incrementally larger portions of the test suites. The test suites are continuously updated as new failure conditions and corner cases are discovered, and they are integrated with any regression tests that are developed. Unit tests are maintained along with the rest of the software source code and generally integrated into the build process (with inherently interactive tests being relegated to a partially manual build acceptance process). The ultimate goal of this test process is to achieve continuous deployment where software updates can be published to the public frequently.   A sample testing cycle Although variations exist between organizations, there is a typical cycle for testing. The sample below is common among organizations employing the Waterfall development model. • Requirements analysis: Testing should begin in the requirements phase of the software development life cycle. During the design phase, testers work with developers in determining what aspects of a design are testable and with what parameters those tests work. • Test planning: Test strategy, test plan, testbed creation. Since many activities will be carried out during testing, a plan is needed. • Test development: Test procedures, test scenarios, test cases, test datasets, test scripts to use in testing software. • Test execution: Testers execute the software based on the plans and test documents then report any errors found to the development team. • Test reporting: Once testing is completed, testers generate metrics and make final reports on their test effort and whether or not the software tested is ready for release. • Test result analysis: Or Defect Analysis, is done by the development team usually along with the client, in order to decide what defects should be treated, fixed, rejected (i.e. found software working properly) or deferred to be dealt with later. • Defect Retesting: Once a defect has been dealt with by the development team, it is retested by the testing team. AKA Resolution testing. • Regression testing: It is common to have a small test program built of a subset of tests, for each integration of new, modified, or fixed software, in order to ensure that the latest delivery has not ruined anything, and that the software product as a whole is still working correctly. • Test Closure: Once the test meets the exit criteria, the activities such as capturing the key outputs, lessons learned, results, logs, documents related to the project are archived and used as a reference for future projects.
Software testing 10 Automated testing Many programming groups are relying more and more on automated testing, especially groups that use test-driven development. There are many frameworks to write tests in, and continuous integration software will run tests automatically every time code is checked into a version control system. While automation cannot reproduce everything that a human can do (and all the ways they think of doing it), it can be very useful for regression testing. However, it does require a well-developed test suite of testing scripts in order to be truly useful. Testing tools Program testing and fault detection can be aided significantly by testing tools and debuggers. Testing/debug tools include features such as: • Program monitors, permitting full or partial monitoring of program code including: • Instruction set simulator, permitting complete instruction level monitoring and trace facilities • Program animation, permitting step-by-step execution and conditional breakpoint at source level or in machine code • Code coverage reports • Formatted dump or symbolic debugging, tools allowing inspection of program variables on error or at chosen points • Automated functional GUI testing tools are used to repeat system-level tests through the GUI • Benchmarks, allowing run-time performance comparisons to be made • Performance analysis (or profiling tools) that can help to highlight hot spots and resource usage Some of these features may be incorporated into an Integrated Development Environment (IDE). • A regression testing technique is to have a standard set of tests, which cover existing functionality that result in persistent tabular data, and to compare pre-change data to post-change data, where there should not be differences, using a tool like diffkit. Differences detected indicate unexpected functionality changes or "regression". Measurement in software testing Usually, quality is constrained to such topics as correctness, completeness, security, but can also include more technical requirements as described under the ISO standard ISO/IEC 9126, such as capability, reliability, efficiency, portability, maintainability, compatibility, and usability. There are a number of frequently-used software measures, often called metrics, which are used to assist in determining the state of the software or the adequacy of the testing. Testing artifacts Software testing process can produce several artifacts. Test plan A test specification is called a test plan. The developers are well aware what test plans will be executed and this information is made available to management and the developers. The idea is to make them more cautious when developing their code or making additional changes. Some companies have a higher-level document called a test strategy. Traceability matrix A traceability matrix is a table that correlates requirements or design documents to test documents. It is used to change tests when the source documents are changed, or to verify that the test results are correct.
Software testing 11 Test case A test case normally consists of a unique identifier, requirement references from a design specification, preconditions, events, a series of steps (also known as actions) to follow, input, output, expected result, and actual result. Clinically defined a test case is an input and an expected result. This can be as pragmatic as for condition x your derived result is y, whereas other test cases described in more detail the input scenario and what results might be expected. It can occasionally be a series of steps (but often steps are contained in a separate test procedure that can be exercised against multiple test cases, as a matter of economy) but with one expected result or expected outcome. The optional fields are a test case ID, test step, or order of execution number, related requirement(s), depth, test category, author, and check boxes for whether the test is automatable and has been automated. Larger test cases may also contain prerequisite states or steps, and descriptions. A test case should also contain a place for the actual result. These steps can be stored in a word processor document, spreadsheet, database, or other common repository. In a database system, you may also be able to see past test results, who generated the results, and what system configuration was used to generate those results. These past results would usually be stored in a separate table. Test script The test script is procedure, or a programing code that replicate the user actions. Initially the term was derived from the product of work created by automated regression test tools. Test Case will be a baseline to create test scripts using a tool or a program. Test suite The most common term for a collection of test cases is a test suite. The test suite often also contains more detailed instructions or goals for each collection of test cases. It definitely contains a section where the tester identifies the system configuration used during testing. A group of test cases may also contain prerequisite states or steps, and descriptions of the following tests. Test data In most cases, multiple sets of values or data are used to test the same functionality of a particular feature. All the test values and changeable environmental components are collected in separate files and stored as test data. It is also useful to provide this data to the client and with the product or a project. Test harness The software, tools, samples of data input and output, and configurations are all referred to collectively as a test harness. Certifications Several certification programs exist to support the professional aspirations of software testers and quality assurance specialists. No certification currently offered actually requires the applicant to demonstrate the ability to test software. No certification is based on a widely accepted body of knowledge. This has led some to declare that the testing field is not ready for certification. Certification itself cannot measure an individuals productivity, their skill, or practical knowledge, and cannot guarantee their competence, or professionalism as a tester. Software testing certification types • Exam-based: Formalized exams, which need to be passed; can also be learned by self-study [e.g., for ISTQB or QAI] • Education-based: Instructor-led sessions, where each course has to be passed [e.g., International Institute for Software Testing (IIST)]. Testing certifications • Certified Associate in Software Testing (CAST) offered by the QAI 
Software testing 12 • CATe offered by the International Institute for Software Testing • Certified Manager in Software Testing (CMST) offered by the QAI  • Certified Software Tester (CSTE) offered by the Quality Assurance Institute (QAI) • Certified Software Test Professional (CSTP) offered by the International Institute for Software Testing • CSTP (TM) (Australian Version) offered by K. J. Ross & Associates • ISEB offered by the Information Systems Examinations Board • ISTQB Certified Tester, Foundation Level (CTFL) offered by the International Software Testing Qualification Board   • ISTQB Certified Tester, Advanced Level (CTAL) offered by the International Software Testing Qualification Board   • TMPF TMap Next Foundation offered by the Examination Institute for Information Science • TMPA TMap Next Advanced offered by the Examination Institute for Information Science Quality assurance certifications • CMSQ offered by the Quality Assurance Institute (QAI). • CSQA offered by the Quality Assurance Institute (QAI) • CSQE offered by the American Society for Quality (ASQ) • CQIA offered by the American Society for Quality (ASQ) Controversy Some of the major software testing controversies include: What constitutes responsible software testing? Members of the "context-driven" school of testing believe that there are no "best practices" of testing, but rather that testing is a set of skills that allow the tester to select or invent testing practices to suit each unique situation. Agile vs. traditional Should testers learn to work under conditions of uncertainty and constant change or should they aim at process "maturity"? The agile testing movement has received growing popularity since 2006 mainly in commercial circles,  whereas government and military software providers use this methodology but also the traditional test-last models (e.g. in the Waterfall model). Exploratory test vs. scripted Should tests be designed at the same time as they are executed or should they be designed beforehand? Manual testing vs. automated Some writers believe that test automation is so expensive relative to its value that it should be used sparingly. More in particular, test-driven development states that developers should write unit-tests of the XUnit type before coding the functionality. The tests then can be considered as a way to capture and implement the requirements. Software design vs. software implementation Should testing be carried out only at the end or throughout the whole process? Who watches the watchmen? The idea is that any form of observation is also an interaction—the act of testing can also affect that which is being tested.
Software testing 13 References  Exploratory Testing (http:/ / www. kaner. com/ pdfs/ ETatQAI. pdf), Cem Kaner, Florida Institute of Technology, Quality Assurance Institute Worldwide Annual Software Testing Conference, Orlando, FL, November 2006  Software Testing (http:/ / www. ece. cmu. edu/ ~koopman/ des_s99/ sw_testing/ ) by Jiantao Pan, Carnegie Mellon University  Leitner, A., Ciupa, I., Oriol, M., Meyer, B., Fiva, A., "Contract Driven Development = Test Driven Development - Writing Test Cases" (http:/ / se. inf. ethz. ch/ people/ leitner/ publications/ cdd_leitner_esec_fse_2007. pdf), Proceedings of ESEC/FSE07: European Software Engineering Conference and the ACM SIGSOFT Symposium on the Foundations of Software Engineering 2007, (Dubrovnik, Croatia), September 2007  Software errors cost U.S. economy $59.5 billion annually (http:/ / www. abeacha. com/ NIST_press_release_bugs_cost. htm), NIST report  Myers, Glenford J. (1979). The Art of Software Testing. John Wiley and Sons. ISBN 0-471-04328-1.  Company, Peoples Computer (1987). "Dr. Dobbs journal of software tools for the professional programmer" (http:/ / books. google. com/ ?id=7RoIAAAAIAAJ). Dr. Dobbs journal of software tools for the professional programmer (M&T Pub) 12 (1–6): 116. .  Gelperin, D.; B. Hetzel (1988). "The Growth of Software Testing". CACM 31 (6). ISSN 0001-0782.  until 1956 it was the debugging oriented period, when testing was often associated to debugging: there was no clear difference between testing and debugging. Gelperin, D.; B. Hetzel (1988). "The Growth of Software Testing". CACM 31 (6). ISSN 0001-0782.  From 1957–1978 there was the demonstration oriented period where debugging and testing was distinguished now - in this period it was shown, that software satisfies the requirements. Gelperin, D.; B. Hetzel (1988). "The Growth of Software Testing". CACM 31 (6). ISSN 0001-0782.  The time between 1979–1982 is announced as the destruction oriented period, where the goal was to find errors. Gelperin, D.; B. Hetzel (1988). "The Growth of Software Testing". CACM 31 (6). ISSN 0001-0782.  1983–1987 is classified as the evaluation oriented period: intention here is that during the software lifecycle a product evaluation is provided and measuring quality. Gelperin, D.; B. Hetzel (1988). "The Growth of Software Testing". CACM 31 (6). ISSN 0001-0782.  From 1988 on it was seen as prevention oriented period where tests were to demonstrate that software satisfies its specification, to detect faults and to prevent faults. Gelperin, D.; B. Hetzel (1988). "The Growth of Software Testing". CACM 31 (6). ISSN 0001-0782.  Kaner, Cem; Falk, Jack and Nguyen, Hung Quoc (1999). Testing Computer Software, 2nd Ed.. New York, et al: John Wiley and Sons, Inc.. pp. 480 pages. ISBN 0-471-35846-0.  Kolawa, Adam; Huizinga, Dorota (2007). Automated Defect Prevention: Best Practices in Software Management (http:/ / www. wiley. com/ WileyCDA/ WileyTitle/ productCd-0470042125. html). Wiley-IEEE Computer Society Press. pp. 41–43. ISBN 0470042125. .  Kolawa, Adam; Huizinga, Dorota (2007). Automated Defect Prevention: Best Practices in Software Management (http:/ / www. wiley. com/ WileyCDA/ WileyTitle/ productCd-0470042125. html). Wiley-IEEE Computer Society Press. p. 86. ISBN 0470042125. .  Section 1.1.2, Certified Tester Foundation Level Syllabus (http:/ / www. istqb. org/ downloads/ syllabi/ SyllabusFoundation. pdf), International Software Testing Qualifications Board  Kaner, Cem; James Bach, Bret Pettichord (2001). Lessons Learned in Software Testing: A Context-Driven Approach. Wiley. p. 4. ISBN 0-471-08112-4.  McConnell, Steve (2004). Code Complete (2nd ed.). Microsoft Press. pp. 29. ISBN 0-7356-1967-0.  Principle 2, Section 1.3, Certified Tester Foundation Level Syllabus (http:/ / www. bcs. org/ upload/ pdf/ istqbsyll. pdf), International Software Testing Qualifications Board  Tran, Eushiuan (1999). "Verification/Validation/Certification" (http:/ / www. ece. cmu. edu/ ~koopman/ des_s99/ verification/ index. html). In Koopman, P.. Topics in Dependable Embedded Systems. USA: Carnegie Mellon University. . Retrieved 2008-01-13.  see D. Gelperin and W.C. Hetzel  Introduction (http:/ / www. bullseye. com/ coverage. html#intro), Code Coverage Analysis, Steve Cornett  Laycock, G. T. (1993) (PostScript). The Theory and Practice of Specification Based Software Testing (http:/ / www. mcs. le. ac. uk/ people/ gtl1/ thesis. ps. gz). Dept of Computer Science, Sheffield University, UK. . Retrieved 2008-02-13.  Bach, James (June 1999). "Risk and Requirements-Based Testing" (http:/ / www. satisfice. com/ articles/ requirements_based_testing. pdf) (PDF). Computer 32 (6): 113–114. . Retrieved 2008-08-19.  Savenkov, Roman (2008). How to Become a Software Tester. Roman Savenkov Consulting. p. 159. ISBN 978-0-615-23372-7.  http:/ / www. computer. org/ portal/ web/ swebok/ html/ ch5#Ref2. 1  http:/ / www. computer. org/ portal/ web/ swebok/ html/ ch5#Ref2. 2  Binder, Robert V. (1999). Testing Object-Oriented Systems: Objects, Patterns, and Tools. Addison-Wesley Professional. p. 45. ISBN 0-201-80938-9.  Beizer, Boris (1990). Software Testing Techniques (Second ed.). New York: Van Nostrand Reinhold. pp. 21,430. ISBN 0-442-20672-0.  IEEE (1990). IEEE Standard Computer Dictionary: A Compilation of IEEE Standard Computer Glossaries. New York: IEEE. ISBN 1559370793.  van Veenendaal, Erik. "Standard glossary of terms used in Software Testing" (http:/ / www. astqb. org/ educational-resources/ glossary. php#A). . Retrieved 17 June 2010.  Globalization Step-by-Step: The World-Ready Approach to Testing. Microsoft Developer Network (http:/ / msdn. microsoft. com/ en-us/ goglobal/ bb688148)  e)Testing Phase in Software Testing:- (http:/ / www. etestinghub. com/ testing_lifecycles. php#2)
Software testing 14  Myers, Glenford J. (1979). The Art of Software Testing. John Wiley and Sons. pp. 145–146. ISBN 0-471-04328-1.  Dustin, Elfriede (2002). Effective Software Testing. Addison Wesley. p. 3. ISBN 0-20179-429-2.  Marchenko, Artem (November 16, 2007). "XP Practice: Continuous Integration" (http:/ / agilesoftwaredevelopment. com/ xp/ practices/ continuous-integration). . Retrieved 2009-11-16.  Gurses, Levent (February 19, 2007). "Agile 101: What is Continuous Integration?" (http:/ / www. jacoozi. com/ blog/ ?p=18). . Retrieved 2009-11-16.  Pan, Jiantao (Spring 1999). "Software Testing (18-849b Dependable Embedded Systems)" (http:/ / www. ece. cmu. edu/ ~koopman/ des_s99/ sw_testing/ ). Topics in Dependable Embedded Systems. Electrical and Computer Engineering Department, Carnegie Mellon University. .  IEEE (1998). IEEE standard for software test documentation. New York: IEEE. ISBN 0-7381-1443-X.  Kaner, Cem (2001). "NSF grant proposal to "lay a foundation for significant improvements in the quality of academic and commercial courses in software testing"" (http:/ / www. testingeducation. org/ general/ nsf_grant. pdf) (pdf). .  Kaner, Cem (2003). "Measuring the Effectiveness of Software Testers" (http:/ / www. testingeducation. org/ a/ mest. pdf) (pdf). .  Black, Rex (December 2008). Advanced Software Testing- Vol. 2: Guide to the ISTQB Advanced Certification as an Advanced Test Manager. Santa Barbara: Rocky Nook Publisher. ISBN 1933952369.  Quality Assurance Institute (http:/ / www. qaiglobalinstitute. com/ )  International Institute for Software Testing (http:/ / www. testinginstitute. com/ )  K. J. Ross & Associates (http:/ / www. kjross. com. au/ cstp/ )  "ISTQB" (http:/ / www. istqb. org/ ). .  "ISTQB in the U.S." (http:/ / www. astqb. org/ ). .  EXIN: Examination Institute for Information Science (http:/ / www. exin-exams. com)  American Society for Quality (http:/ / www. asq. org/ )  context-driven-testing.com (http:/ / www. context-driven-testing. com)  Article on taking agile traits without the agile method. (http:/ / www. technicat. com/ writing/ process. html)  “We’re all part of the story” (http:/ / stpcollaborative. com/ knowledge/ 272-were-all-part-of-the-story) by David Strom, July 1, 2009  IEEE article about differences in adoption of agile trends between experienced managers vs. young students of the Project Management Institute (http:/ / ieeexplore. ieee. org/ Xplore/ login. jsp?url=/ iel5/ 10705/ 33795/ 01609838. pdf?temp=x). See also Agile adoption study from 2007 (http:/ / www. ambysoft. com/ downloads/ surveys/ AgileAdoption2007. ppt)  Willison, John S. (April 2004). "Agile Software Development for an Agile Force" (http:/ / web. archive. org/ web/ 20051029135922/ http:/ / www. stsc. hill. af. mil/ crosstalk/ 2004/ 04/ 0404willison. html). CrossTalk (STSC) (April 2004). Archived from the original (http:/ / www. stsc. hill. af. mil/ crosstalk/ 2004/ 04/ 0404willison. htm) on unknown. .  IEEE article on Exploratory vs. Non Exploratory testing (http:/ / ieeexplore. ieee. org/ iel5/ 10351/ 32923/ 01541817. pdf?arnumber=1541817)  An example is Mark Fewster, Dorothy Graham: Software Test Automation. Addison Wesley, 1999, ISBN 0-201-33140-3.  Article referring to other links questioning the necessity of unit testing (http:/ / java. dzone. com/ news/ why-evangelising-unit-testing-)  Microsoft Development Network Discussion on exactly this topic (http:/ / channel9. msdn. com/ forums/ Coffeehouse/ 402611-Are-you-a-Test-Driven-Developer/ ) External links • Software testing tools and products (http://www.dmoz.org/Computers/Programming/Software_Testing/ Products_and_Tools/) at the Open Directory Project • "Software that makes Software better" Economist.com (http://www.economist.com/science/tq/displaystory. cfm?story_id=10789417) • Automated software testing metrics including manual testing metrics (http://idtus.com/img/ UsefulAutomatedTestingMetrics.pdf)
15 Black-box testingBlack-box testingBlack-box testing is a method of software testing that tests thefunctionality of an application as opposed to its internal structuresor workings (see white-box testing). Specific knowledge of the Black box diagramapplications code/internal structure and programming knowledgein general is not required. Test cases are built aroundspecifications and requirements, i.e., what the application is supposed to do. It uses external descriptions of thesoftware, including specifications, requirements, and design to derive test cases. These tests can be functional ornon-functional, though usually functional. The test designer selects valid and invalid inputs and determines thecorrect output. There is no knowledge of the test objects internal structure.This method of test can be applied to all levels of software testing: unit, integration, functional, system andacceptance. It typically comprises most if not all testing at higher levels, but can also dominate unit testing as well.Test design techniquesTypical black-box test design techniques include:• Decision table testing• All-pairs testing• State transition tables• Equivalence partitioning• Boundary value analysis. In this approach, the domain of a program is partitioned into a set of equivalence classes. The partitioning is done such that the behaviour of the program is similar to every input data belonging to the same equivalence class.HackingIn penetration testing, black-box testing refers to a methodology where an ethical hacker has no knowledge of thesystem being attacked. The goal of a black-box penetration test is to simulate an external hacking or cyber warfareattack.External links• BCS SIGIST (British Computer Society Specialist Interest Group in Software Testing): Standard for Software Component Testing , Working Draft 3.4, 27. April 2001.References http:/ / www. testingstandards. co. uk/ Component%20Testing. pdf
Exploratory testing 16 Exploratory testing Exploratory testing is an approach to software testing that is concisely described as simultaneous learning, test design and test execution. Cem Kaner, who coined the term in 1983, now defines exploratory testing as "a style of software testing that emphasizes the personal freedom and responsibility of the individual tester to continually optimize the quality of his/her work by treating test-related learning, test design, test execution, and test result interpretation as mutually supportive activities that run in parallel throughout the project." While the software is being tested, the tester learns things that together with experience and creativity generates new good tests to run. Exploratory testing is often thought of as a black box testing technique. Instead, those who have studied it consider it a test approach that can be applied to any test technique, at any stage in the development process. The key is not the test technique nor the item being tested or reviewed; the key is the cognitive engagement of the tester, and the testers responsibility for managing his or her time. History Exploratory testing has always been performed by skilled testers. In the early 1990s, ad hoc was too often synonymous with sloppy and careless work. As a result, a group of test methodologists (now calling themselves the Context-Driven School) began using the term "exploratory" seeking to emphasize the dominant thought process involved in unscripted testing, and to begin to develop the practice into a teachable discipline. This new terminology was first published by Cem Kaner in his book Testing Computer Software and expanded upon in Lessons Learned in Software Testing. Exploratory testing can be as disciplined as any other intellectual activity. Description Exploratory testing seeks to find out how the software actually works, and to ask questions about how it will handle difficult and easy cases. The quality of the testing is dependent on the testers skill of inventing test cases and finding defects. The more the tester knows about the product and different test methods, the better the testing will be. To further explain, comparison can be made of freestyle exploratory testing to its antithesis scripted testing. In this activity test cases are designed in advance. This includes both the individual steps and the expected results. These tests are later performed by a tester who compares the actual result with the expected. When performing exploratory testing, expectations are open. Some results may be predicted and expected; others may not. The tester configures, operates, observes, and evaluates the product and its behaviour, critically investigating the result, and reporting information that seems like to be a bug (which threatens the value of the product to some person) or an issue (which threatens the quality of the testing effort). In reality, testing almost always is a combination of exploratory and scripted testing, but with a tendency towards either one, depending on context. According to Cem Kaner & James Bach, exploratory testing is more a mindset or "...a way of thinking about testing" than a methodology. They also say that it crosses a continuum from slightly exploratory (slightly ambiguous or vaguely scripted testing) to highly exploratory (freestyle exploratory testing). The documentation of exploratory testing ranges from documenting all tests performed to just documenting the bugs. During pair testing, two persons create test cases together; one performs them, and the other documents. Session-based testing is a method specifically designed to make exploratory testing auditable and measurable on a wider scale. Exploratory testers often use tools, including screen capture or video tools as a record of the exploratory session, or tools to quickly help generate situations of interest, e.g. James Bachs Perlclip.
Exploratory testing 17 Benefits and drawbacks The main advantage of exploratory testing is that less preparation is needed, important bugs are found quickly, and at execution time, the approach tends to be more intellectually stimulating than execution of scripted tests. Another major benefit is that testers can use deductive reasoning based on the results of previous results to guide their future testing on the fly. They do not have to complete a current series of scripted tests before focusing in on or moving on to exploring a more target rich environment. This also accelerates bug detection when used intelligently. Another benefit is that, after initial testing, most bugs are discovered by some sort of exploratory testing. This can be demonstrated logically by stating, "Programs that pass certain tests tend to continue to pass the same tests and are more likely to fail other tests or scenarios that are yet to be explored." Disadvantages are that tests invented and performed on the fly cant be reviewed in advance (and by that prevent errors in code and test cases), and that it can be difficult to show exactly which tests have been run. Freestyle exploratory test ideas, when revisited, are unlikely to be performed in exactly the same manner, which can be an advantage if it is important to find new errors; or a disadvantage if it is more important to repeat specific details of the earlier tests. This can be controlled with specific instruction to the tester, or by preparing automated tests where feasible, appropriate, and necessary, and ideally as close to the unit level as possible. Usage Exploratory testing is particularly suitable if requirements and specifications are incomplete, or if there is lack of time.  The approach can also be used to verify that previous testing has found the most important defects. References  Kaner, Falk, and Nguyen, Testing Computer Software (Second Edition), Van Nostrand Reinhold, New York, 1993. p. 6, 7-11.  Cem Kaner, A Tutorial in Exploratory Testing (http:/ / www. kaner. com/ pdfs/ QAIExploring. pdf), p. 36.  Cem Kaner, A Tutorial in Exploratory Testing (http:/ / www. kaner. com/ pdfs/ QAIExploring. pdf), p. 37-39, 40- .  Kaner, Cem; Bach, James; Pettichord, Bret (2001). Lessons Learned in Software Testing. John Wiley & Sons. ISBN 0471081124.  Cem Kaner, James Bach, Exploratory & Risk Based Testing, www.testingeducation.org (http:/ / www. testingeducation. org), 2004, p. 10  Cem Kaner, James Bach, Exploratory & Risk Based Testing, www.testingeducation.org (http:/ / www. testingeducation. org), 2004, p. 14  Bach, James (2003). "Exploratory Testing Explained" (http:/ / www. satisfice. com/ articles/ et-article. pdf). satisfice.com. p. 7. . Retrieved October 23, 2010.  Kaner, Cem (2008). "A Tutorial in Exploratory Testing" (http:/ / www. kaner. com/ pdfs/ QAIExploring. pdf). kaner.com. p. 37, 118. . Retrieved October 23, 2010. External links • James Bach, Exploratory Testing Explained (http://www.satisfice.com/articles/et-article.pdf) • Cem Kaner, James Bach, The Nature of Exploratory Testing (http://www.testingeducation.org/a/nature.pdf), 2004 • Cem Kaner, James Bach, The Seven Basic Principles of the Context-Driven School (http://www. context-driven-testing.com) • Jonathan Kohl, Exploratory Testing: Finding the Music of Software Investigation (http://www.methodsandtools. com/archive/archive.php?id=65), Kohl Concepts Inc., 2007 • Chris Agruss, Bob Johnson, Ad Hoc Software Testing (http://www.testingcraft.com/ad_hoc_testing.pdf)
San Francisco depot 18 San Francisco depot San Francisco depot is a mnemonic for the SFDPO software exploratory testing heuristic. SFDPO stands for Structure, Function, Data, Platform and Operations. Each of these represents a different aspect of a software product. Structure Structure is what the entire product is. This is its physical files, utility programs, physical materials such as user docs, specifications and design docs, etc. Function Function is what the product does. This is the products features. How does it handle errors? What is its UI? How does it interface with the operating system? Data Data is what the product processes. What kinds of input does it process? This can be input from the user, the file system, etc. What kind of output or reports does it generate? Does it come with default data? Is any of its input sensitive to timing or sequencing? Platform Platform is what the product depends upon. What operating systems and related service packs, browsers, runtime libraries, plug-ins, languages and locales, etc. does it run on? Does the user need to configure the environment? Does it depend on third-party components? Operations Operations are scenarios in which the product will be used. Who are the applications users and what are their patterns and sequences of input? Where and how will they use it? What are the different ways a user can use the products features? External links • How Do You Spell Testing?  References  http:/ / www. satisfice. com/ articles/ sfdpo. shtml
Session-based testing 19 Session-based testing Session-based testing is a software test method that aims to combine accountability and exploratory testing to provide rapid defect discovery, creative on-the-fly test design, management control and metrics reporting. The method can also be used in conjunction with Scenario testing. Session-based testing was developed in 2000 by Jonathan and James Bach. Session-based testing can be used to introduce measurement and control to an immature test process, and can form a foundation for significant improvements in productivity and error detection. Session-based testing can offer benefits when formal requirements are not present, incomplete, or changing rapidly. Elements of session-based testing Charter A charter is a goal or agenda for a test session. Charters are created by the test team prior to the start of testing, but may be added or changed at any time. Often charters are created from a specification, test plan, or by examining results from previous test sessions. Session An uninterrupted period of time spent testing, ideally lasting one to two hours. Each session is focused on a charter, but testers can also explore new opportunities or issues during this time. The tester creates and executes test cases based on ideas, heuristics or whatever frameworks to guide them and records their progress. This might be through the use of written notes, video capture tools or by whatever method as deemed appropriate by the tester. Session report The session report records the test session. Usually this includes: • Charter. • Area tested. • Detailed notes on how testing was conducted. • A list of any bugs found. • A list of issues (open questions, product or project concerns) • Any files the tester used or created to support their testing • Percentage of the session spent on the charter vs investigating new opportunities. • Percentage of the session spent on: • Testing - creating and executing tests. • Bug investigation / reporting. • Session setup or other non-testing activities. • Session Start time and duration.
Session-based testing 20 Debrief A debrief is a short discussion between the manager and tester (or testers) about the session report. Jon Bach, one of the co-creators of session based test management, uses the aconymn PROOF to help structure his debriefing. PROOF stands for:- • Past. What happened during the session? • Results. What was achieved during the session? • Obstacles. What got in the way of good testing? • Outlook. What still needs to be done? • Feelings. How does the tester feel about all this? Parsing results With a standardized Session Report, software tools can be used to parse and store the results as aggregate data for reporting and metrics. This allows reporting on the number of sessions per area or a breakdown of time spent on testing, bug investigation, and setup / other activities. Planning Testers using session-based testing can adjust their testing daily to fit the needs of the project. Charters can be added or dropped over time as tests are executed and/or requirements change. References  http:/ / www. satisfice. com/ articles/ sbtm. pdf External links • Session-Based Test Management Site (http://www.satisfice.com/sbtm/) • How to Manage and Measure ET (http://www.quardev.com/content/whitepapers/ how_measure_exploratory_testing.pdf) • Session-Based Test Lite (http://www.quardev.com/articles/sbt_lite) • Adventures in Session-Based Testing (http://www.workroom-productions.com/papers/AiSBTv1.2.pdf) • Session-Based Test Management (http://www.satisfice.com/articles/sbtm.pdf) • Applying Session-Based Testing to Medical Software (http://www.devicelink.com/mddi/archive/03/05/003. html) • Web application based on Session-based testing software test method (http://sites.google.com/site/ sessionbasedtester/)
Scenario testing 21 Scenario testing Scenario testing is a software testing activity that uses scenario tests, or simply scenarios, which are based on a hypothetical story to help a person think through a complex problem or system for a testing environment. The ideal scenario has five key characteristics: it is (a) a story that is (b) motivating, (c) credible, (d) complex, and (e) easy to evaluate . These tests are usually different from test cases in that test cases are single steps whereas scenarios cover a number of steps. Test suites and scenarios can be used in concert for complete system testing. References  "An Introduction to Scenario Testing" (http:/ / www. kaner. com/ pdfs/ ScenarioIntroVer4. pdf). Cem Kaner. . Retrieved 2009-05-07. External links • Introduction to Scenario Testing (http://www.kaner.com/pdfs/ScenarioIntroVer4.pdf) Equivalence partitioning Equivalence partitioning (also called Equivalence Class Partitioning or ECP ) is a software testing technique that divides the input data of a software unit into partitions of data from which test cases can be derived. In principle, test cases are designed to cover each partition at least once. This technique tries to define test cases that uncover classes of errors, thereby reducing the total number of test cases that must be developed. In rare cases equivalence partitioning is also applied to outputs of a software component, typically it is applied to the inputs of a tested component. The equivalence partitions are usually derived from the requirements specification for input attributes that influence the processing of the test object. An input has certain ranges which are valid and other ranges which are invalid. Invalid data here does not mean that the data is incorrect, it means that this data lies outside of specific partition. This may be best explained by the example of a function which takes a parameter "month". The valid range for the month is 1 to 12, representing January to December. This valid range is called a partition. In this example there are two further partitions of invalid ranges. The first invalid partition would be <= 0 and the second invalid partition would be >= 13. ... -2 -1 0 1 .............. 12 13 14 15 ..... --------------|-------------------|--------------------- invalid partition 1 valid partition invalid partition 2 The testing theory related to equivalence partitioning says that only one test case of each partition is needed to evaluate the behaviour of the program for the related partition. In other words it is sufficient to select one test case out of each partition to check the behaviour of the program. To use more or even all test cases of a partition will not find new faults in the program. The values within one partition are considered to be "equivalent". Thus the number of test cases can be reduced considerably. An additional effect of applying this technique is that you also find the so called "dirty" test cases. An inexperienced tester may be tempted to use as test cases the input data 1 to 12 for the month and forget to select some out of the invalid partitions. This would lead to a huge number of unnecessary test cases on the one hand, and a lack of test cases for the dirty ranges on the other hand. The tendency is to relate equivalence partitioning to so called black box testing which is strictly checking a software component at its interface, without consideration of internal structures of the software. But having a closer look at the subject there are cases where it applies to grey box testing as well. Imagine an interface to a component which
Equivalence partitioning 22 has a valid range between 1 and 12 like the example above. However internally the function may have a differentiation of values between 1 and 6 and the values between 7 and 12. Depending upon the input value the software internally will run through different paths to perform slightly different actions. Regarding the input and output interfaces to the component this difference will not be noticed, however in your grey-box testing you would like to make sure that both paths are examined. To achieve this it is necessary to introduce additional equivalence partitions which would not be needed for black-box testing. For this example this would be: ... -2 -1 0 1 ..... 6 7 ..... 12 13 14 15 ..... --------------|---------|----------|--------------------- invalid partition 1 P1 P2 invalid partition 2 valid partitions To check for the expected results you would need to evaluate some internal intermediate values rather than the output interface. It is not necessary that we should use multiple values from each partition. In the above scenario we can take -2 from invalid partition 1, 6 from valid partition, and 15 from invalid partition 2. Equivalence partitioning is not a stand alone method to determine test cases. It has to be supplemented by boundary value analysis. Having determined the partitions of possible inputs the method of boundary value analysis has to be applied to select the most effective test cases out of these partitions. References • The Testing Standards Working Party website  • Parteg , a free test generation tool that is combining test path generation from UML state machines with equivalence class generation of input values.  Burnstein, Ilene (2003), Practical Software Testing, Springer-Verlag, p. 623, ISBN 0-387-95131-8  http:/ / www. testingstandards. co. uk  http:/ / parteg. sourceforge. net
Boundary-value analysis 23 Boundary-value analysis Boundary value analysis is a software testing technique in which tests are designed to include representatives of boundary values. Values on the minimum and maxiumum edges of an equivalence partition are tested. The values could be either input or output ranges of a software component. Since these boundaries are common locations for errors that result in software faults they are frequently exercised in test cases. Application The expected input and output values to the software component should be extracted from the component specification. The values are then grouped into sets with identifiable boundaries. Each set, or partition, contains values that are expected to be processed by the component in the same way. Partitioning of test data ranges is explained in the equivalence partitioning test case design technique. It is important to consider both valid and invalid partitions when designing test cases. For an example, if the input values were months of the year expressed as integers, the input parameter month might have the following partitions: ... -2 -1 0 1 .............. 12 13 14 15 ..... --------------|-------------------|------------------- invalid partition 1 valid partition invalid partition 2 The boundary between two partitions is the place where the behavior of the application changes and is not a real number itself. The boundary value is the minimum (or maximum) value that is at the boundary. The number 0 is the maximum number in the first partition, the number 1 is the minimum value in the second partition, both are boundary values. Test cases should be created to generate inputs or outputs that will fall on and to either side of each boundary, which results in two cases per boundary. The test cases on each side of a boundary should be in the smallest increment possible for the component under test, for an integer this is 1, but the input was a decimal with 2 places then it would be .01. In the example above there are boundary values at 0,1 and 12,13 and each should be tested. Boundary value analysis does not require invalid partitions. Take an example where a heater is turned on if the temperature is 10 degrees or colder. There are two partitions (temperature<=10, temperature>10) and two boundary values to be tested (temperature=10, temperature=11). Where a boundary value falls within the invalid partition the test case is designed to ensure the software component handles the value in a controlled manner. Boundary value analysis can be used throughout the testing cycle and is equally applicable at all testing phases. References • The Testing Standards Working Party  website.
All-pairs testing 24 All-pairs testing All-pairs testing or pairwise testing is a combinatorial software testing method that, for each pair of input parameters to a system (typically, a software algorithm), tests all possible discrete combinations of those parameters. Using carefully chosen test vectors, this can be done much faster than an exhaustive search of all combinations of all parameters, by "parallelizing" the tests of parameter pairs. The number of tests is typically O(nm), where n and m are the number of possibilities for each of the two parameters with the most choices. The reasoning behind all-pairs testing is this: the simplest bugs in a program are generally triggered by a single input parameter. The next simplest category of bugs consists of those dependent on interactions between pairs of parameters, which can be caught with all-pairs testing. Bugs involving interactions between three or more parameters are progressively less common, whilst at the same time being progressively more expensive to find by exhaustive testing, which has as its limit the exhaustive testing of all possible inputs. Many testing methods regard all-pairs testing of a system or subsystem as a reasonable cost-benefit compromise between often computationally infeasible higher-order combinatorial testing methods, and less exhaustive methods which fail to exercise all possible pairs of parameters. Because no testing technique can find all bugs, all-pairs testing is typically used together with other quality assurance techniques such as unit testing, symbolic execution, fuzz testing, and code review. Notes  Black, Rex (2007). Pragmatic Software Testing: Becoming an Effective and Efficient Test Professional. New York: Wiley. p. 240. ISBN 978-0-470-12790-2.  D.R. Kuhn, D.R. Wallace, A.J. Gallo, Jr. (June 2004). "Software Fault Interactions and Implications for Software Testing" (http:/ / csrc. nist. gov/ groups/ SNS/ acts/ documents/ TSE-0172-1003-1. pdf). IEEE Trans. on Software Engineering 30 (6). .  (2010) Practical Combinatorial Testing. SP 800-142. (http:/ / csrc. nist. gov/ groups/ SNS/ acts/ documents/ SP800-142-101006. pdf). Natl. Inst. of Standards and Technology. (Report). External links • Combinatorialtesting.com; Includes clearly written introductions to pairwise and other, more thorough, methods of combinatorial testing (http://www.combinatorialtesting.com) • Hexawise.com - Pairwise test case generating tool with both free and commercial versions (also provides more thorough 3-way, 4-way, 5-way, and 6-way coverage solutions) (http://hexawise.com/) • [TESTCOVER.com - http://testcover.com/pub/background/stareast2008.ppt Pairwise Testing Comes of Age - Review including history, examples, issues, research] • TestersDesk.com - Online tool platform has a Pairwise Test-case Generator (http://www.testersdesk.com) • Pairwise Testing: Combinatorial Test Case Generation (http://www.pairwise.org/) • Pairwise testing (http://www.developsense.com/testing/PairwiseTesting.html) • All-pairs testing (http://www.mcdowella.demon.co.uk/allPairs.html) • Pairwise and generalized t-way combinatorial testing (http://csrc.nist.gov/acts/) • TestApi - the API library for testing, providing a variation generation API (http://testapi.codeplex.com)
Fuzz testing 25 Fuzz testing Fuzz testing or fuzzing is a software testing technique, often automated or semi-automated, that involves providing invalid, unexpected, or random data to the inputs of a computer program. The program is then monitored for exceptions such as crashes or failing built-in code assertions. Fuzzing is commonly used to test for security problems in software or computer systems. The term first originates from a class project at the University of Wisconsin 1988 although similar techniques have been used in the field of quality assurance, where they are referred to as robustness testing, syntax testing or negative testing. There are two forms of fuzzing program; mutation-based and generation-based, which can be employed as white-, grey- or black-box testing. File formats and network protocols are the most common targets of testing, but any type of program input can be fuzzed. Interesting inputs include environment variables, keyboard and mouse events, and sequences of API calls. Even items not normally considered "input" can be fuzzed, such as the contents of databases, shared memory, or the precise interleaving of threads. For the purpose of security, input that crosses a trust boundary is often the most interesting. For example, it is more important to fuzz code that handles the upload of a file by any user than it is to fuzz the code that parses a configuration file that is accessible only to a privileged user. History The term "fuzz" or "fuzzing" originates from a 1988 class project at the University of Wisconsin, taught by Professor Barton Miller. The assignment was titled "Operating System Utility Program Reliability - The Fuzz Generator".  The project developed a basic command-line fuzzer to test the reliability of Unix programs by bombarding them with random data until they crashed. The test was repeated in 1995, expanded to include testing of GUI-based tools (X Windows), network protocols, and system library APIs. Follow-on work included testing command- and GUI-based applications on both Windows and MacOS X. One of the earliest examples of fuzzing dates from before 1983. "The Monkey" was a Macintosh application developed by Steve Capps prior to 1983. It used journaling hooks to feed random events into Mac programs, and was used to test for bugs in MacPaint. Uses Fuzz testing is often employed as a black-box testing methodology in large software projects where a budget exists to develop test tools. Fuzz testing is one of the techniques which offers a high benefit to cost ratio. The technique can only provide a random sample of the systems behavior, and in many cases passing a fuzz test may only demonstrate that a piece of software can handle exceptions without crashing, rather than behaving correctly. This means fuzz testing is an assurance of overall quality, rather than a bug-finding tool, and not a substitute for exhaustive testing or formal methods. As a gross measurement of reliability, fuzzing can suggest which parts of a program should get special attention, in the form of a code audit, application of static analysis, or partial rewrites.
Fuzz testing 26 Types of bugs As well as testing for outright crashes, fuzz testing is used to find bugs such as assertion failures and memory leaks (when coupled with a memory debugger). The methodology is useful against large applications, where any bug affecting memory safety is likely to be a severe vulnerability. Since fuzzing often generates invalid input it is used for testing error-handling routines, which are important for software that does not control its input. Simple fuzzing can be thought of as a way to automate negative testing. Fuzzing can also find some types of "correctness" bugs. For example, it can be used to find incorrect-serialization bugs by complaining whenever a programs serializer emits something that the same programs parser rejects. It can also find unintentional differences between two versions of a program or between two implementations of the same specification. Techniques Fuzzing programs fall into two different categories. Mutation based fuzzers mutate existing data samples to create test data while generation based fuzzers define new test data based on models of the input. The simplest form of fuzzing technique is sending a stream of random bits to software, either as command line options, randomly mutated protocol packets, or as events. This technique of random inputs still continues to be a powerful tool to find bugs in command-line applications, network protocols, and GUI-based applications and services. Another common technique that is easy to implement is mutating existing input (e.g. files from a test suite) by flipping bits at random or moving blocks of the file around. However, the most successful fuzzers have detailed understanding of the format or protocol being tested. The understanding can be based on a specification. A specification-based fuzzer involves writing the entire array of specifications into the tool, and then using model-based test generation techniques in walking through the specifications and adding anomalies in the data contents, structures, messages, and sequences. This "smart fuzzing" technique is also known as robustness testing, syntax testing, grammar testing, and (input) fault injection.    The protocol awareness can also be created heuristically from examples using a tool such as Sequitur . These fuzzers can generate test cases from scratch, or they can mutate examples from test suites or real life. They can concentrate on valid or invalid input, with mostly-valid input tending to trigger the "deepest" error cases. There are two limitations of protocol-based fuzzing based on protocol implementations of published specifications: 1) Testing cannot proceed until the specification is relatively mature, since a specification is a prerequisite for writing such a fuzzer; and 2) Many useful protocols are proprietary, or involve proprietary extensions to published protocols. If fuzzing is based only on published specifications, test coverage for new or proprietary protocols will be limited or nonexistent. Fuzz testing can be combined with other testing techniques. White-box fuzzing uses symbolic execution and constraint solving. Evolutionary fuzzing leverages feedback from code coverage, effectively automating the approach of exploratory testing. Reproduction and isolation So as to be able to reproduce errors, fuzzing software will often record the input data it produces, usually before applying it to the software. If the computer crashes outright, the test data is preserved. If the fuzz stream is pseudo-random number-generated, the seed value can be stored to reproduce the fuzz attempt. Once a bug is found, some fuzzing software will help to build a test case, which is used for debugging, using testcase reduction tools such as Delta or Lithium.